This invention relates to reinforced metal tubes, and will be described with particular reference to a hollow aluminum ball bat having a carbon composite core. The articles and methods disclosed are not however limited to ball bats and have widespread application wherever high strength, lightweight tubes are required and, more particularly, where the tubular structure is comprised of a protective metal overlayer and a fiber composite underlayer for added strength.
Examples where such structures are particularly useful include many sports applications in addition to ball bats such as bicycle frames and seat posts, shafts for golf clubs, sailboat and windsurfing masts and booms, and hockey sticks. A particularly useful application of such tubes is the seat post for off road or all terrain bicycles where a long post enables one to have a smaller frame which gives a better ride.
Over the years, a great number of hollow metal baseball bat designs have been disclosed. See, for example, U.S. Pat. No. 4,248,425, Easton, issued Feb. 3, 1981. Some of these designs include inserts which are intended to dampen vibration and increase the impact resistance of the bat when striking a ball. Examples of these types of designs are disclosed in U.S. Pat. No. 3,861,682, issued to H. Fujii on Jun. 15, 1976, and U.S. Pat. No. 4,323,239 issued to J. Ishii on Apr. 6, 1982.
Various composite tubular elements in which a metal tube is provided with an exterior wrapping of carbon reinforcing fibers are disclosed in U.S. Pat. Nos. 4,173,670 issued Nov. 6, 1979; 4,131,701 issued Dec. 26, 1978; 4,084,819 issued Apr. 18, 1978; 4,082,277 issued Apr. 4, 1978; and 4,023,801 issued May 17, 1977; all to Richard L Van Auken.
Some attempts have also been made to coat or wrap the exterior of a metal bat with materials intended to enhance batting performance. An example of this type of design is disclosed in U.S. Pat. No. 4,025,377, issued to Y. Tanikawa on May 24, 1977.
In general, exterior wrappings and coatings on tubular metal articles do not provide a significant improvement in articles subject to external impacts or other forces such as metal ball bats or bicycle parts. This is particularly true for bicycle seat tubes which are clamped inside of a frame tube because carbon fibers on the exterior of the seat tube will become damaged and lose structural integrity if the frame tube is clamped directly on these fibers.
Accordingly, it is an object of the present invention to provide a new and improved strong and lightweight structure comprised of a metal tube having internal carbon fiber reinforcing.
It is another object of the present invention to provide a new metal ball bat having a very high rate of wall recovery during impact.